1. Field of the Invention
The present invention relates to a multi-type air conditioner, and more particularly, to a system for detecting a mis-connected state between communication lines for a multi-type air conditioner capable of preventing a damage of the system by judging a mis-connected state between communication lines based on a temperature response characteristic of an indoor unit refrigerant pipe according to an opening of an electronic expansion valve, and a method thereof.
2. Description of the Background Art
Generally, an air conditioner serves to control a temperature, a humidity, air stream, and a clean degree for a comfortable indoor circumstance. The air conditioner is classified into an integral-type air conditioner and a separated-type air conditioner according to a unit construction. The integral-type air conditioner is constructed as an indoor unit and an outdoor unit are received in a single case. On the contrary, the separated-type air conditioner is constructed as an outdoor unit constituted with a compressor and a condenser is separated from an indoor unit constituted with an evaporator. Additionally, there is an air conditioner for cooling and heating capable of selectively performing a cooling operation and a heating operation by switching a flow path of a refrigerant by a flow path switching valve provided at the air conditioner. Recently, a multi-type air conditioner having a plurality of indoor units for cooling or heating each space of an indoor room is being increased. The multi-type air conditioner is constructed as a plurality of outdoor units each having a plurality of compressors corresponding to a load of the indoor unit are connected to one another in parallel.
FIG. 1 is an exemplary view showing an outdoor unit of a multi-type air conditioner in accordance with the background art.
As shown, the multi-type air conditioner comprises a plurality of outdoor units (11a˜11n), and a plurality of indoor units (not shown).
Each outdoor unit 11a˜11n comprises a first compressor 13a and a second compressor 13b constructed as one pair, a four-way valve 21 for switching a flow path of a refrigerant, an outdoor heat exchanger 25 for heat-exchanging a refrigerant, and a common accumulator 27 for providing a gaseous refrigerant to the first compressor 13a and the second compressor 13b. 
A discharge pipe 15 for discharging a refrigerant is provided at each upper region of the first compressor 13a and the second compressor 13b. Also, a suction pipe 17 connected to the common accumulator 27 for sucking a refrigerant is provided at each lower region of the first compressor 13a and the second compressor 13b. An oil balancing pipe 19 for flowing oil with balance is connected between the first compressor 13a and the second compressor 13b. 
Each compressor is provided with an oil separator 31 and a check valve 33 at the discharge side thereof. Also, each separator 31 is provided with an oil returning path 35 for returning oil to the suction side of each compressor.
Each check valve 33 is provided with a four-way valve 21 for switching a flow path of a refrigerant at a lower side thereof. One port of the four-way valve 21 is connected to the outdoor heat exchanger 25, another port thereof is connected to the common accumulator 27, and the other port thereof is connected to a connection pipe 41 connected to the indoor unit.
The outdoor heat exchanger 25 is provided with a receiver 37 at one side thereof along a flow direction of a refrigerant. The receiver 37 and the connection pipe 41 are respectively provided with a service valve 43a and a service valve 43b at one side thereof. Each one side of the service valves 43a and 43b is connected to a main refrigerant pipe 45 for connecting the outdoor units 11a˜11n one another.
FIG. 2 is an exemplary view showing a multi-type air conditioner having an arbitrary outdoor unit and a plurality of indoor units connected to the outdoor unit in accordance with the background art.
As shown, the multi-type air conditioner comprises an outdoor unit and a plurality of indoor units connected to the outdoor unit. The outdoor unit is connected to the plural indoor units by communication lines, thereby controlling an air conditioning of the plural indoor units.
In case that the multi-type air conditioner is installed in the same building, a plurality of outdoor units can be connected to a plurality of indoor units by communication lines crossed to one another. Accordingly, a mis-connection between the communication lines may occur.
FIG. 3 is an exemplary view showing a mis-connected state between communication lines in a multi-type air conditioner in accordance with the background art.
As shown, an indoor unit 1 receives a refrigerant from an outdoor unit A, and receives an operation control command from an outdoor unit B. Also, an indoor unit 4 receives a refrigerant from the outdoor unit B, and receives an operation control command from the outdoor unit A. Accordingly, if a mis-connection between the communication lines of the outdoor units occurs due to a cross connection therebetween, a control signal of one outdoor unit is transmitted to an indoor unit controlled by another outdoor unit. Therefore, the system is stopped while being operated thus to cause the user's inconvenience and to cause the system to be mechanically damaged.